1. Field of the Invention
The present invention relates to a dustproof fabric and to a method of manufacturing the same. More particularly, the present invention relates to a dustproof smock worn by technicians in the clean room and to a method of manufacturing the fabric of the smock.
2. Description of the Related Art
Clean rooms are being used more often in a great number of different areas including semiconductor fabrication facilities. The requirements for maintaining cleanliness in semiconductor fabrication clean rooms are stringent. Even the smocks worn by technicians in clean room environments must be carefully designed and manufactured to prevent the clean room from being contaminated by dust or moisture emanating from the bodies of the technicians themselves (now referred to as xe2x80x9cparticlesxe2x80x9d).
The first semiconductor devices to be manufactured were not nearly as highly-integrated as the semiconductor devices which are manufactured today. In the past, the clean rooms were maintained at a cleanliness class level of between 10 k and 100 k, and the smocks worn by the technicians in the clean rooms were made of nylon or polyester taffeta.
However, the semiconductor device fabrication process continues to become more and more affected by the environmental conditions existing in the place in which the process takes place. Such conditions include the level of particulate contaminants, the electrostatic level of the air, etc. Accordingly, more attention has been paid to the material of the smocks worn by the technicians in the clean room. In this respect, polyester smocks have been adopted for use in the clean room.
Recently, highly integrated semiconductor devices having critical dimensions on the order of sub-microns, such as the 64M DRAM, 256M DRAM, etc., have been developed. The clean rooms in which such devices are made must be maintained at a cleanliness class of less than 10 k. This requirement has brought about an even greater scrutiny of the fabric from which the clean room smock is made.
Even the ultra-fine filaments of the nylon taffeta or polyester taffeta of the conventional clean room smocks could not prevent an unsatisfactory amount of moisture or fine particulates from emanating from workers"" bodies into the clean room environment. The warp and weft of such fabric is just too great. Therefore, such fabric was treated with a moisture-permeable and water-proof, water-repellent coating or laminate of polyurethane resin or fluoric resin. Fabric treated in this way is shown in FIG. 1, and is manufactured by The Dupont Company of Delaware under-the trademark GORETEX.
Referring now to FIG. 1, a polyester fabric 3 woven from aligned conductive yarns 2 is coated with a polyurethane and/or fluoric resin film 1. As shown in FIG. 2, particles emanating from one""s body cannot pass through the coated resin film 1, but moisture from the body can pass through fine pores of the fabric. Accordingly, the fabric is moisture-permeable. On the other hand, water molecules having a relatively large size cannot permeate the pores 14 of the coating layer 15 and may become stuck. Thus, the moisture permeability decreases, and the comfort level of wearing the fabric is somewhat compromised. The comfort level is even lower when the resin layer 1, 15 is located at the side of the fabric which contacts the skin.
An object of the present invention is to overcome one or more of the problems, limitations and disadvantages of the related art.
Accordingly, a first specific object of the present invention is to provide a dustproof fabric which is impermeable to particles of 0.1 microns or larger.
Another specific object of the present invention is to provide a dustproof fabric having a relatively high degree of water-permeability and which is very comfortable when worn.
To achieve these objects, the dustproof fabric of the present invention comprises three integrated layers. The inner layer is of a knitted fabric. The intermediate layer is formed of a non-microporous polyurethane resin exhibiting a high degree of moisture absorbency. The outer layer is formed of a high density polyester woven fabric having warps and wefts of respective sets of spaced apart conductive yarns.
The knit fabric of the inner layer is preferably a warp-knitted fabric of nylon tricot having good strength and resilience.
The intermediate layer and the inner layer are preferably attached by dots of hot-melt adhesive so that the fabric retains a sufficient degree of flexibility. On the other hand, the intermediate layer and the outer layer can be attached by dots or by a thin coating of adhesive.
The high density polyester woven fabric of the outer layer may also comprise ultra-fine yarns having a filament denier of 0.1 or less. Such yarns can be produced by the so-called sea and island type or separation type of conjugate spinning.
As far as the pattern of the high-density polyester woven fabric of the outer layer is concerned, a 2/1 Twill and in particular, a Herringbone twill is preferable.
The objects of the invention are also achieved by a method of manufacturing a dustproof fabric comprising the steps of: (a) manufacturing a woven fabric, having a warp density of 140 to 170 yarns per inch and a weft density of 90 to 130 yarns per inch, from polyester yarns having a yarn denier in a range of 50 to 100 and conductive yarns having a yarn denier in a range of 15 to 30, with the conductive yarns aligned with one another and spaced apart in both the warp and weft; (b) coating release paper with non-micro porous polyurethane resin exhibiting a high degree of moisture absorbency, attaching the woven fabric to the polyurethane, and drying the same (c) aging the integrated layers sufficiently to facilitate a cross-linking reaction in the polyurethane resin layer, and detaching the release paper therefrom; and (d) attaching nylon knit fabric to the polyurethane layer, and aging the same.
In addition, the high-density woven fabric of the outer layer is preferably subjected to an anti-static treatment of a per se known type.
A clean room smock of the fabric described above is made dustproof by the polyurethane film provided on the high-density woven fabric.
In fact, ultra-fine particles from the human body, which range in size from 0.001 to 0.1 xcexcm, are prevented from passing through the smock by the intermediate layer of polyurethane film according to the present invention.
Moreover, because of the high degree of moisture permeability exhibited by the polyurethane layer, a smock made from the dustproof fabric is very comfortable to wear.